class Container {
    static of (value) {
        return new Container(value)
    }

    constructor(value) {
        this._value = value
    }

    map(fn) {
        return Container.of(fn(this._value))
    }
}

/**
 * 对空值进行效验的函子
 * */ 
class Maybe {
    static of (value) {
        return new Maybe(value)
    }

    isNothing() {
        return this._value === null || this._value === undefined
    }

    constructor(value) {
        this._value = value
    }

    map(fn) {
        return this.isNothing() ? this : Maybe.of(fn(this._value))
    }
}

module.exports = { Maybe, Container }
